The Knights played their part in a Division Two contest that contained some good rugby league, scoring four tries through Charlie Barker (two), Liam Sheridan and Connor Wilson, with Barker adding a conversion, but lost 40-18.
The sin-binning of Jake Tyson for a professional foul in the 33rd minute proved to be pivotal.
Heworth, who were 10-4 ahead at that stage, had stretched their lead to 26-4 by the time Tyson returned and went on to win convincingly with the help of four Billy Sturdy tries.
Adam Dent, meanwhile, crossed twice, with Danny Allen and Fraser West popping in and George Elliott kicking four goals.
Here's Rob's images from the match: